March 11, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion

Evaluation of Seismic Activities for February 2014

1 Major Seismic Activities

There was no remarkable activity.

• Seismic Activities for All of Japan in February 2014 (Magnitude 4.0 or over)

to supplementary reports

2 Nationwide Seismic Activities by Region

(1) Hokkaido Region

There was no remarkable activity.

• Hokkaido Region

to supplementary reports

(2) Tohoku Region

* On February 6, there was a magnitude (M) 5.3 earthquake at a depth of approximately 40 km, offshore Miyagi prefecture. The focal mechanism showed a reverse fault with a compression axis in an NW-SE direction. This event occurred within the Pacific plate.

* On February 8, at 02:18 (JST), there was a M5.0 earthquake at a depth of approximately 50 km, offshore Fukushima prefecture. On the same day at 11:34, there was also a M4.8 earthquake. The focal mechanism of these events showed a reverse fault with a compression axis in a WNW-ESE direction. These events occurred on the boundary between the Pacific and the continental plates

• Tohoku Region
• Aftershock Activities of the 2011 off the Pacific Coast of Tohoku Earthquake (1)
• Aftershock Activities of the 2011 off the Pacific Coast of Tohoku Earthquake (2)
• Crustal Movements After the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0) (Horizontal) -One Month-
• Crustal Movements After the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0) (Vertical) -One Month-
• Crustal Movements After the 2011 off the Pacific Coast of Tohoku Earthquake (M9.0)
• Crustal Movements Before and After the 2011 off the Pacific Coast of Tohoku Earthquake
• Earthquake Offshore Miyagi Prefecture on February 6
• Earthquake Offshore Fukushima Prefecture on February 8 (at 02:18)
• Earthquake Offshore Fukushima Prefecture on February 8 (at 11:34)

to supplementary reports

(3) Kanto-Chubu Region

* On February 11, there was a M5.3 earthquake at a depth of approximately 90 km, offshore south of the Boso peninsula. The focal mechanism had a compression axis in an NW-SE direction. This event occurred within the Pacific plate.

* In the GNSS data for the Tokai region, there have been no changes of activity which are likely to be associated with the Tokai earthquake.

• Kanto - Chubu Region
• Earthquake Offshore South of Boso Peninsula on February 11
• Continuous GNSS Monitoring in the Area from Kakegawa to Omaezaki
• Secular Variation of Benchmark 2595 (Omaezaki City)

to supplementary reports

(4) Kinki-Chugoku-Shikoku Region

There was no remarkable activity.

• Kinki-Chugoku-Shikoku Region

to supplementary reports

(5) Kyushu-Okinawa Region

* On February 2, there was a M4.5 earthquake at a depth of approximately 45 km under the ocean near Amami Oshima. The focal mechanism showed a reverse fault with a compression axis in an NNW-SSE direction. This event occurred on the boundary between the Philippine Sea and the continental plates.

* On February 6, there was a M5.0 earthquake at a depth of approximately 50 km under the ocean near Miyakojima. The focal mechanism had a compression axis in an E-W direction.

• Kyushu Region
• Earthquake under the Ocean near Amami Oshima on February 2
• Okinawa Region
• Earthquake under the Ocean near Miyakojma on February 6

to supplementary reports

Supplement

* On March 3, there was a M6.4 earthquake at a depth of approximately 120 km, offshore north-west of Okinawa Main Island. The focal mechanism had a compression axis in a direction of the subducting Philippine Sea plate. This event occurred within the Philippine Sea plate.

* On March 3, there was a M5.0 earthquake at a depth of approximately 45 km under the ocean near Okinawa Main Island. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction.

• Earthquake offshore north-west of Okinawa Main Island on March 3
• Earthquake under the Ocean near Okinawa Main Island on March 3

to supplementary reports

Note: [ ] was the regional name of the epicenter used in the Japan Meteorological Agency announcement.
     GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.

Supplementary Information to the Evaluation of Seismic Activities for February 2014

March 11, 2014
Earthquake Research Committee

1 Major Seismic Activities

The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during February 2014.

• M4.0 or greater: 79 (91 events in January, 2014)
• M5.0 or greater: 10 (8 events in January, 2014)
• M6.0 or greater: 0 (0 events in January, 2014)

(reference)

• M4.0 or greater: 73 / month (Median number of earthquakes over the past 10 years from 1998 through 2007)
• M5.0 or greater: 9 / month (Median number of earthquakes over the past 35 years from 1973 through 2007)
• M6.0 or greater: 1.4 / month, approximately 17 / year (Average number of earthquakes over the past 84 years from 1924 through 2007)

The following events for the period from Feburuary 2013 to late January 2014 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities".

to the text

2 Nationwide Seismic Activities by Region

(1) Hokkaido Region

There is no supplementary information for the Hokkaido region.

to the text

(2) Tohoku Region

There is no supplementary information for the Tohoku region.

to the text

(3) Seismic activities and crustal deformations associated with the 2011 off the Pacific Coast of Tohoku Earthquake

(Reference: Evaluation of Seismic Activities after the 2011 off the Pacific Coast of Tohoku Earthquake)

(4) Kanto-Chubu Region

–"In the GNSS data for the Tokai region, there have been no changes of activity which are likely to be associated with the Tokai earthquake":
(This evaluation is in agreement with the views presented at the regular meeting on February 24 of the Assessment Committee for Areas under Intensified Measures against Earthquake Disaster (reference below).)

(Reference)

Recent seismic and crustal activity in the Tokai region and its vicinity (Seismological and Volcanological Department, Japan Meteorological Agency, February 24, 2014)
"No changes of activity which are likely to be associated with the Tokai earthquake have been observed until now. (Excerpted)"

to the text

(5) Kinki-Chugoku-Shikoku Region

There is no supplementary information for Kinki-Chugoku-Shikoku region.

to the text

(6) Kyushu-Okinawa Region

There is no supplementary information for Kyushu-Okinawa region.

to the text